Zeolites and zeolite-like materials are porous crystalline materials made of tetrahedral oxide building blocks, bonded through tetrahedral corner oxygen atoms. Many natural and synthetic zeolites or zeolite-like materials with distinct crystal structures are currently known and are recognizable by distinct and characteristic X-ray diffraction patterns. The zeolite or zeolite-like crystal structures contain cages, cavities and channels that are characteristic for each crystal framework type, making zeolites and zeolite-like materials useful as shape and size selective adsorbents and catalysts. Zeolites and zeolite-like materials are used in many commercial processes, particularly in petroleum refining and petrochemical processes.
For petroleum refining, zeolites having large pore sizes and/or a three-dimensional pore network containing large cavities are of particular interest, as such large pore materials allow good diffusivity throughout the crystal structure.
Recently a research group from the University of Valencia reported the preparation of a new large pore zeolite, known as ITQ-21, which exhibits good performance as a catalyst for converting petroleum feedstocks into diesel, gasoline and other hydrocarbons of interest to the petrochemical industry (A. Corma et al., Nature, Vol. 418, August 2002, pp. 514-517; U.S. Pat. Nos. 6,849,248; 6,998,037; 7,008,612 and US Patent Application Publication Nos. 2005/0165,267; 2005/0192469; 2005/018259, all incorporated herewith by reference). As reported by A. Corma, et al., ITQ-21 is a porous crystalline material having a three-dimensional channel system, with circular openings comprising 12-membered rings. The three straight channels intersect at large inner cages, which are nearly spherical, with about 1.18 nm in diameter. ITQ-21 is identified in U.S. Pat. Nos. 6,849,248; 6,998,037; 7,008,612 and in US Patent Application Publication Nos. 2005/0165,267; 2005/0192469; 2005/018259 as a crystalline material giving, in its calcined form, an X-ray diffraction pattern with the most characteristic diffraction peaks identified in Table 1, in which d are interplanar spaces in Angstrom and the relative intensity of the lines is calculated as a percentage with respect to the most intense peak, with vs being a very strong relative intensity of 80-100, m being a medium intensity of 40-60, and w being a weak intensity of 20-40.
TABLE 12θ (°)dRelative(±0.3)(±0.3 A)Intensity6.413.64vs11.27.87vs18.44.82w19.64.55m21.64.11m26.33.41m29.33.04w
Up to now, ITQ-21 has been prepared from reaction mixtures containing water, optionally an oxide or another source of at least one trivalent X, conveniently Al, an oxide or another source of a tetravalent element or elements Y, conveniently Si, a source of Ge, such as GeO2, and N(16)-methylsparteinium hydroxide as structure directing agent. The reaction mixture can comprise fluoride or hydroxyl ions. So far, N(16)-methylsparteinium hydroxide is the only structure-directing agent reported as successfully producing ITQ-21.
We have now found that crystalline zeolites iso-structural with ITQ-21 may be obtained from reaction mixtures that use organic structure directing agents other than N(16)-methylsparteinium hydroxide. One of the advantages of these organic structure directing agents is that they are conveniently available for commercial scale synthesis. Another advantage, is that these structure directing agents allow the manufacture of very small crystallites of zeolites that are iso-structural with ITQ-21. Other advantages of the invention are discussed in the detailed description of the invention and illustrative examples.